In previous works, axion electrodynamics in three-dimensional $p+is$ superconductors is discussed by borrowing the results from superconducting Dirac systems. However, in this work, based on a systematic path integral approach, we show that the axion electrodynamics in $p+is$ superconductors exhibits a nonrelativistic form, which is different from the superconducting Dirac and Weyl systems. More precisely, the induced electric field does not enter into the axion action, and gauge invariance is ensured by the combination of the electric potential and the Nambu-Goldstone phase mode. Furthermore, unlike the axion angle in the Dirac case which is equal to the difference between the superconducting phases on the two Fermi surfaces of different helicities, the axion angle in the present case contains an additional sinusoidal term. As applications of the derived nonrelativistic axion electrodynamics, physical effects related to vortex lines and Witten effect are discussed. Our work reveals the differences for axion electrodynamics between the relativistic and nonrelativistic systems.

The paper offers an approach to ab initio calculations for predicting the electron transport properties of solid-state metals in a case of nonequilibrium heating. Formulas for the electrical resistivity (also static conductivity) and thermal conductivity of metals at different electron and lattice temperatures were derived within a method proposed by Allen [Phys. Rev. B 17, 3725 (1978)] for the solution of the Boltzmann transport equation. The approach works well under equilibrium heating too when electron and lattice temperatures are equal. It performs most effectively if it is necessary to allow for the Fermi smearing of the electron distribution function over quantum states and the energy dependence of the electron-phonon spectral function. Four metals—Cu, Ag, Au and Pd—are considered as examples. We succeeded to reproduce well the temperature dependencies of electrical resistivity and thermal conductivity of studied metals in a wide range of temperatures under equilibrium heating. For the nonequilibrium regime of heating, calculations reproduce quite well the temporal evolution of the static electrical conductivity of gold, observed in recent experiments for the interaction of thin gold foils with ultrashort laser pulses.

The widely distributed GHz to THz spin dynamics of antiferromagnets, combined with the recent demonstration of spin pumping, underscores the potential of dynamic antiferromagnetic devices. Here, we report antiferromagnetic spin pumping from a van der Waals antiferromagnetic insulator ${\text{CrCl}}_3$. Spin pumping driven by the Néel vector and the net magnetization has been verified, by adjusting the angle between two sublattice magnetizations from ${180}^{\circ }$ to $0^{\circ }$ while measuring the spin pumping voltages. An enhancement of acoustic mode spin current while decreasing the angle is observed, which proves the spin current is driven by the net magnetization. However, the optical mode spin current increases first and then decreases with the decreasing angle, which proves the optical mode spin current is driven by the Néel vector. These findings reveal the underlying contributions of $\mathit{n}$ in antiferromagnets, and its distinctive role in antiferromagnetic spin pumping.

We show that the Higgs mode of superconductors can couple with spin dynamics in the presence of a static spin-splitting field and Rashba spin-orbit coupling. The Higgs-spin coupling dramatically modifies the spin susceptibility near the superconducting critical temperature and consequently enhances the spin pumping effect in a ferromagnetic insulator/superconductor bilayer system. We show that this effect can be detected by measuring the magnon transmission rate and the magnon-induced voltage generated by the inverse spin Hall effect.

High-harmonic generation (HHG) in solids is a fundamental nonlinear phenomenon, which can be efficiently controlled by modifying system parameters such as doping level and temperature. To correctly predict the dependence of HHG on these parameters, consistent theoretical formulation of the light-matter coupling is crucial. Recently, contributions to the current that are often missing in the HHG analysis based on the semiconductor Bloch equations have been pointed out [Wilhelm et al., Phys. Rev. B 103, 125419 (2021)]. In this paper, by systematically analyzing the doping and gap-size dependence of HHG in gapped graphene, we discuss the practical impact of such terms. In particular, we focus on the role of the current $J_{\mathrm{ra}}^{\left(2\right)}$, which originates from the change of the intraband dipole via interband transition. When the gap is small and the system is close to half filling, intraband and interband currents mostly cancel, thus suppressing the HHG signal—an important property that is broken when neglecting $J_{\mathrm{ra}}^{\left(2\right)}$. Furthermore, without $J_{\mathrm{ra}}^{\left(2\right)}$, the doping and gap-size dependence of HHG becomes qualitatively different from the full evaluation. Our results demonstrate the importance of the consistent expression of the current to study the parameter dependence of HHG for the small gap systems.

The third-order nonlinear Hall effect induced by the Berry-connection polarizability tensor has been observed in Weyl semimetals ${\mathrm{T}}_d\text{−}{\mathrm{MoTe}}_2$ as well as ${\mathrm{T}}_d\text{−}{\mathrm{TaIrTe}}_4$. The experiments were performed on bulk samples, and the results were interpreted with the semiclassical Boltzmann approach. Beyond the bulk limit, we develop a quantum nonlinear transport theory to investigate the third-order Hall response of a four-terminal setup with time-reversal symmetry in the quantum regime. The quantum nonlinear theory is verified on a model system of monolayer ${\mathrm{MoTe}}_2$, and numerical results on the angle-resolved Hall currents are qualitatively consistent with the experiment. More importantly, quantum signatures of the third-order Hall effect are revealed, which are independent of the system symmetry. The first quantum signature is quantum enhancement of the third-order Hall current, which is characterized by sharp current peaks whose magnitudes are three orders larger than those of the first-order Hall current. Such quantum enhancement originates from quantum interference in coherent transport, and it can be easily destroyed by the dephasing effect. The second quantum signature is disorder-induced enhancement of the third-order Hall current for weak disorders. Our findings reveal quantum characteristics of the third-order Hall effect, and we propose feasible ways to enhance it in nanoscale systems. The quantum third-order theory developed in this paper provides a general formalism for describing nonlinear coherent transport properties in multiterminal devices, regardless of the system symmetry.

We study the Magnus transport in a gapped two-dimensional electron gas with Rashba spin-orbit coupling using semiclassical Boltzmann transport formalism. Apart from its signature in the charge transport coefficients, the inclusion of Magnus velocity in the spin current operator enables us to study Magnus spin transport in the system. In particular, we study the roles of mass gap and Fermi surface topology on the behavior of Magnus Hall and Nernst conductivities and their spin counterparts. We find that the Magnus spin Hall conductivity vanishes in the limit of zero gap, unlike the universal spin Hall conductivity ${\sigma }_s=e/\left(8\pi \right)$. The Magnus spin currents with spin polarization perpendicular to the applied bias (electrical/thermal) are finite while with polarization along the bias vanishes. Each Magnus conductivity displays a plateau as Fermi energy sweeps through the gap and has peaks (whose magnitudes decrease with the gap) when the Fermi energy is at the gap edges.

The anomalous transport properties of Heusler compounds have become a hot spot of research in recent years due to their unique band structure and possible application in spintronics. In this paper, we report the anomalous Hall effect in a polycrystalline NiCoMnGa quaternary Heusler compound by experimental means and theoretical calculations. The experimental anomalous Hall conductivity (AHC) was found to be about 256 S/cm at 10 K with an intrinsic contribution of $\sim 121$ S/cm. The analysis of Hall data reveals the presence of both extrinsic and intrinsic contributions in the anomalous Hall effect. Our theoretical calculations show that a pair of spin-orbit coupled bands formed by the band splitting due to spin-orbit interaction at the Fermi level produces a finite Berry flux in the system that provides an intrinsic AHC of about 100 S/cm, which is in good agreement with the experiment.

In the heavy fermion system, development of the Kondo coherence usually occurs as a crossover behavior. However, accurate definition of the onset temperature for complete formation of the heavy quasiparticles is to some extent controversial. Here, the electronic structure of the quasi-two-dimensional Kondo lattice ${\mathrm{CeSb}}_2$ has been studied by high resolution angle-resolved photoemission spectroscopy (ARPES) and dynamical mean-field theory approach combined with density functional theory. A heavy quasiparticle band, which originates from the hybridization between $f$ electrons and conduction electrons, has been observed directly. Moreover, temperature-dependent electronic structure study reveals a transition from high-temperature local spins to low-temperature itinerant electrons in ${\mathrm{CeSb}}_2$ and the onset temperature of the hybridized c-f spectral weight revealed by laser-ARPES is consistent with the crossover temperature from transport and magnetic measurements. Our findings are essential for a microscopic understanding of different energy scales in the heavy fermion system and demonstrate the probability of laser-ARPES in studying the bulk 4f-electron properties of Ce-based compounds.

Electron-hole liquids (EHLs), a correlated state of matter and a thermodynamic liquid, have recently been found to exist at room temperature in suspended monolayers of ${\text{MoS}}_2$. Appreciably higher rates of radiative recombination inside the liquid as compared to free excitons hold promise for optoelectronic applications such as broadband lasing. In this paper, we show that leveraging the valley physics in ${\text{MoS}}_2$ may be a route towards achieving tunability of specific characteristics of an EHL, such as emission wavelength, linewidth, and, most importantly, the liquid density. The conditions under which EHLs form, in bulk semiconductors as well as transition metal dichalcogenide (TMDC) monolayers are quite stringent, requiring high crystal purity and cryogenic temperatures in bulk semiconductors, and suspension in monolayers. Using a simple yet powerful model for describing free excitons and show that a phase transition into the EHL state may be feasible in substrate-supported monolayer samples. More repeatable experimental realizations of EHLs may be essential to answer questions regarding the nature of electron-hole correlations and how they may be used to generate nontrivial states of light.

We investigate the response of the optically generated spin current as a function of time at the graphene edge for a possible application of optospintronic devices. The spin current is generated by optically excited edge plasmon in which the induced electric field is rotating on the graphene plane. According to the inverse Faraday effect, the in-plane rotation of electric field generates magnetization in the direction perpendicular to the graphene plane. The diffusive spin current flows by decaying distribution of the magnetization from the edge. By solving the time-dependent, diffusion equation in the presence/absence of the spin-source term, we evaluate the on/off response of spin current. The switching speed becomes fast when the spin-diffusion length is sufficiently large compared with the decaying length of the magnetization.

Coupled-wire constructions have been widely applied to quantum Hall systems and symmetry-protected topological (SPT) phases. In this Letter, we use the coupled one-dimensional nonchiral Luttinger liquids with domain-wall structured mass terms as quantum wires to construct crystalline higher-order topological superconductors (HOTSCs) in two-dimensional (2D) interacting fermionic systems by two representative examples: a $D_4$-symmetric class-D HOTSC and a $C_4$-symmetric class-BDI HOTSC, with Majorana corner modes on the edge. Furthermore, based on the coupled-wire constructions, the quantum phase transitions between different phases of 2D HOTSCs by tuning the interwire coupling are investigated in a straightforward way.

The creation of defect with predetermined optical, chemical, and other characteristics is a powerful tool to enhance the functionalities of materials. Herewith, we utilize density functional theory to understand the microscopic mechanisms of formation of defects in hexagonal boron nitride based on vacancies and substitutional atoms. Through in-depth analysis of the defect-induced band structure and formation energy in varying growth conditions, we uncovered a dominant role of interdefect electron pairing in stabilization of defect complexes. The electron reorganization modifies the exchange component of the electronic interactions which dominates over direct Coulomb repulsion or structural relaxation effects making the combination of acceptor- and donor-type defect centers energetically favorable. Based on an analysis of a large number of defect complexes we develop a simple picture of the inheritance of the electronic properties when individual defects are combined together to form more complex centers.

We report on anomalous light transport in the strong scattering regime. Using low-coherence interferometry, we measure the reflection matrix of titanium dioxide powders, revealing crucial features of strong optical scattering which cannot be observed with transmission measurements: (i) a subdiffusive regime of transport at early times of flight that is a direct consequence of predominant recurrent scattering loops and (ii) a crossover to a conventional, but extremely slow, diffusive regime at long times. These observations support previous predictions that near-field coupling between scatterers prohibits Anderson localization of light in three-dimensional disordered media.

We present a simple way to calculate the time-dependent energy transfer between a general pulse of light and a layered media. Although we argue that trying to define such absorption is, in general, meaningless, our model still improves the standard method by including effects such as chromatic dispersion, more accurate time dependence of absorption, and nonabsorptive effects.

${\mathrm{EuMnSb}}_2$ is a candidate topological material which can be tuned towards a Weyl semimetal, but there are differing reports for its antiferromagnetic (AFM) phases. The coupling of bands dominated by pure Sb layers hosting topological fermions to Mn and Eu magnetic states provides a potential path to tune the topological properties. Here we present single-crystal neutron diffraction, magnetization, and heat-capacity data as well as polycrystalline ${}^{151}\mathrm{Eu}$ Mössbauer data which show that three AFM phases exist as a function of temperature, and we present a detailed analysis of the magnetic structure in each phase. The Mn magnetic sublattice orders into a C-type AFM structure below $T_{{\text{N}}_{\text{Mn}}}=323\left(1\right)\mathrm{K}$ with the ordered Mn magnetic moment ${\mathbf{\mu }}_{\mathit{\text{Mn}}}$ lying perpendicular to the layers. AFM ordering of the Eu sublattice occurs below $T_{{\text{N}}_{\text{Eu1}}}=23\left(1\right)\mathrm{K}$ with the ordered Eu magnetic moment ${\mathit{\mu }}_{\text{Eu}}$ canted away from the layer normal and ${\mathbf{\mu }}_{\mathit{\text{Mn}}}$ retaining its higher temperature order. ${\mathit{\mu }}_{\text{Eu}}$ is ferromagnetically aligned within each Eu layer but exhibits a complicated AFM layer stacking. Both of these higher-temperature phases are described by magnetic space group (MSG) $P{n}^{\prime }{m}^{\prime }{a}^{\prime }$ with the chemical and magnetic unit cells having the same dimensions. Cooling below $T_{{\text{N}}_{\text{Eu2}}}=9\left(1\right)\mathrm{K}$ reveals a third AFM phase where ${\mathbf{\mu }}_{\mathit{\text{Mn}}}$ remains unchanged but ${\mathit{\mu }}_{\text{Eu}}$ develops an additional substantial in-plane canting. This phase has MSG $P11\frac{2_1}{a^{\prime }}$. We also find some evidence of short-range magnetic correlations associated with the Eu between $12\text{K}\lesssim T\lesssim 30\text{K}$. Using the determined magnetic structures, we postulate the signs of nearest-neighbor intralayer and interlayer exchange constants and the magnetic anisotropy within a general Heisenberg model. We then discuss implications of the various AFM states in ${\mathrm{EuMnSb}}_2$ and their potential for tuning topological properties.

The anomalous Hall effect (AHE) can appear in certain antiferromagnetic metals when it is allowed by symmetry. Since the net magnetization is usually small in such anomalous Hall antiferromagnets, it is useful to have other physical indicators of the AHE that have the same symmetry properties as the latter and can be conveniently measured and calculated. Here we propose such indicators named as electronic chiralization (EC), which are constructed using spatial gradients of spin and charge densities in general periodic crystals, and can potentially be measured directly by scattering experiments. Such constructions particularly reveal the important role of magnetic charge in the AHE in unconventional magnetic systems with vanishing net magnetization. Guided by the EC we give two examples of the AHE when magnetic charge is explicitly present: A minimum honeycomb model inspired by the magnetic-charge-ordered phase of kagome spin ice, and skew scattering of two-dimensional Dirac electrons by magnetic charge.

We report results from spin trimer-based cluster quantum Monte Carlo simulations for the thermodynamic properties of two-dimensional frustrated quantum antiferromagnets that are composed of weakly coupled three-spin (trimer) clusters. In particular, we consider the spin-1/2 kagome lattice with a strong breathing distortion, and the triangle-square lattice model proposed previously for the cuprate $\mathrm{La}{}_4\mathrm{Cu}{}_3\mathrm{MoO}{}_{12}$. For both cases, we demonstrate that an appropriately chosen trimer-based computational basis allows us to significantly reduce the quantum Monte Carlo sign problem down to the low-temperature regime. Besides exploring the thermodynamic behavior for the triangle-square lattice model we also assess a mean-field theory based prediction for the onset of chiral order. For the breathing distorted kagome lattice model, we observe a robust two-peak structure in the specific heat, both in the quantum spin liquid and the lattice-nematic regimes.